SPECIAL METHODS. 175 



they have to overcome great difficulties in the small size 

 and ready decomposition of the bodies concerned. There- 

 fore it is not yet certain whether the various organs of the 

 plasma-mass, like the nucleoli or the leucoplasts, consist 

 .always of the same or only of related chemical compounds ; 

 although their behavior with certain staining agents makes 

 the former supposition seem probable for many cases. For 

 ive possess certain staining methods which act with such 

 precision as to render them worthy of places with the best 

 rnicrochemical reactions, and to assure the first place in 

 the investigation of protoplasmic structures to staining 

 methods. But it cannot be doubted that in the immediate 

 future microchemical reactions may be of the greatest 

 importance in the study of the plasma-body. 



In the folloVing pages we will first discuss the methods of 

 recognizing the various inclusions and differentiations of 

 the protoplasm, and then describe some methods which 

 have been used in the study of various general character- 

 istics of the plasma-mass and the cell-sap, and of certain 

 physiological processes. 



i. The Nucleus and its Constituents. 



299. The advances which our knowledge of the morpho- 

 logical characters of the nucleus have made in recent dec- 

 ades are almost exclusively due to staining methods, which 

 makes explicable the fact that the most various natural and 

 artificial dye-stuffs have been tested as to their applicability 

 in this respect, and that innumerable staining methods have 

 been most warmly recommended by their discoverers. 



It cannot be necessary for me to enumerate all 'these 

 methods here, but rather to limit myself to the best of them, 

 which are capable of general application and do not fail in 

 difficult cases. I begin with the enumeration of the most 

 important fixing and staining methods, and add some gen- 

 eral remarks as to the staining of the nucleus in various 

 cells and on the recognition of its various constituents. 



